Konqueror is one of the most advanced file managers for KDE. Thanks to the underlying KDE technologies it can transparently access FTP and SFTP servers, zip files (and other archives), smb (Windows) shares, and even browse and rip audio CDs.
Konqueror makes use of the latest KDE technologies to provide you with a PDF viewer, an FTP client, a text editor, a spreadsheet editor, a word document editor, an SVN client and more without ever needing to open a separate application.
Konqueror comes with a nice set of custom plugins such as an ad blocker, automatic web page translation, user agent switcher, automatic image gallery creation, shell command panel, and more.
It is one of the most customizable applications available.